This work is concerned with the intracellular and surface expression of certain murine antigens, and the relation between the two. TL antigens have been shown to be present on mitochondria and their intracellular expression will be followed after antigenic modulation. BIBLIOGRAPHIC REFERENCES: Weisz-Carrington, P., Poger, M. E., and Lamm, M. E. Secretory immunoglobulins in colonic neoplasms. Amer. J. Path. 85:303, 1976.